Conjugated Polyelectrolytes for Optoelectronic Applications

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

TECHNICAL SUMMARY Conjugated polyelectrolytes are described by a polymer backbone with a polarizable pi-delocalized electronic structure and pendant groups bearing ionic functionalities. These materials thus incorporate the useful optical and electronic attributes of semiconducting and light harvesting polymers with the properties of polyelectrolytes, which are modulated by complex electrostatic interactions. Such a combination of properties opens unique opportunities for designing materials that can be integrated into optoelectronic devices. One attractive target involves the creation of stable p-n junctions, which constitute a cornerstone in the fabrication of inorganic solid state devices. Such a fundamental module in organic counterparts has been difficult to attain due to difficulties in depositing thin films with independent p-doped and n-doped layers. The approach will take advantage of ion migration across polymer bilayers and concomitant formation of covalent bonds for permanently fixing the junction. Specific polymers will be designed and synthesized that have anion receptor groups and solubility properties for multilayer device fabrication. Another opportunity lies in the design, synthesis and applications of conjugated polyzwitterions. These materials are generated by attaching Lewis acids to lone pairs of electrons present along the polymer chain. When this approach is used on a conjugated polymer with a donor/acceptor motif, it is possible to attain large red shifts in the absorption profiles due to the stabilization of charge transfer excited states. Such polymers are essentially unexplored and offer new opportunities in the design of new materials for solar cell fabrication. NON-TECHNICAL SUMMARY Emerging organic optoelectronic technologies require materials with suitable electronic properties that can enable mass fabrication by solution methods, for example similar to those used in the production of photographic film. Conjugated polyelectrolytes are a new class of semiconducting polymers that open opportunities to create modules similar to those widely used with silicon-based technologies. One of the principal goals of this proposal is to integrate these conjugated polyelectrolytes and related materials into diodes and plastic solar cells. The work will include molecular design, materials preparation, examination of physical properties and device fabrication and testing. Students will benefit from a broad scientific perspective, which will serve them well in their future careers. Additionally, international links are in place for raising their awareness to global collaborations. Programs are also in place for educational programs with undergraduate and minority-serving institutions.